In diff tool speak, a visual diff tool is a GUI application. Meld is such a tool: a tool for displaying differences between files (and directories) and also for merging the differences. Meld is programmed in Python.

Like other word processes, OpenOffice.org Writer makes creating tables of contents (ToCs) quick and easy. Unfortunately, it also works with unaesthetic defaults and allows you to make choices that complicate your work flow rather than improving it. Fortunately, Writer is also flexible enough to allow you to produce useful, aesthetic ToCs if you follow a few basic steps.

If you saw yesterday's Tech Tip and were looking for more on using TCP/IP with bash's built-in /dev/tcp device file then read on. Here, we'll both read from, and write to a socket.

Most of us default to wget, curl, netcat and others when in need of network data from the commandline, not knowing, or perhaps forgetting, that bash often provides the support that we need using redirection from /dev/proto/host/port.

I don't do a lot of audio/video stuff with my system, but the other day I had the urge to see if there was some voice synthesis software available on Linux and it turned out that I already had it installed: it's called Festival. Turns out there are a number of voice synthesis and analysis packages available.

If you need a quick web server running and you don't want to mess with setting up apache or something similar, then Python can help. Python comes with a simple builtin HTTP server. With the help of this little HTTP server you can turn any directory in your system into your web server directory. The only thing you need to have installed is Python.

If you're a Vonage user and you'd like to keep tabs on your bill as the month progresses, the script described here can help. The script uses curl to login to your Vonage account and download the web page with your current balance. The balance is then extracted using grep and sed.

Shell Scripts are very useful but not all that fun to look at. They have simple user input and output text. But, there is a way to spice up your scripts and make them a bit more eye catching with a simple program called "Figlet".

Bash functions, unlike functions in most programming languages do not allow you to return a value to the caller. When a bash function ends its return value is its status: zero for success, non-zero for failure. To return values, you can set a global variable with the result, or use command substitution, or you can pass in the name of a variable to use as the result variable. The examples below describe these different mechanisms.

VirtualBox is a free, powerful and versatile virtualization program which is available for Linux, Mac, and Windows hosts, and can virtualize many different Operating Systems. VirtualBox was originally developed by Innotek, but was purchased by Sun and renamed Sun xVM VirtualBox.

The bash function presented here normalizes path names. By normalize I mean it removes unneeded /./ and ../dir sequences. For example, ../d1/./d2/../f1 normalized would be ../d1/f1.

Notify-send is a great application for notifying you when an event has occurred. An event such as a script running to completion. If notify-send is not installed on your machine already, install the package "libnotify1" (or possibly just "libnotify") from your repositories.

In my last article I wrote about accessing a PostgreSQL database in C/C++. In this article, I'm going to discuss performing the same functions in C against an SQLite database. Unlike Postgresql and the supporting libraries, SQLite creates completely self-contained databases that aren't dependant upon a client-server architecture.

Quoting things in bash is quite simple... until it isn't. I've written scripts where I'd swear 90% of the effort was getting bash to quote things correctly.

Using ssh tunnelling I can protect services which are not normally protected and/or encrypted against unauthorized access. In this example I show how I set up a secure connection to my IRC proxy, but you can use this same recipe for other things.

Reading files is no big deal with bash: you just redirect the input to the script or pipe the output of another command into the script, or you could do it inside the script if the file names are pre-determined. You could also use process substitution to pass in the open files (command pipelines actually) from the command line. Another option, the one I describe here, is to just open the files and read (or write) them as you like, as you'd do in other programming languages.

Encrypting files from the command line is simple with gpg. You can use it to encrypt and decrypt files with a password.

You can use the following command line tools to retrieve the make and model of your hard drives without the need to open up your system.

Those of you who watch our Tech Tip Videos may have seen my video on how to fetch the US National Debt at the command line. The script contained here uses the idea I developed there and expands it to fetch the debt twice, with an optional pause in between, and then display the amount that the debt has increased during the pause.

The command deborphan can be used to check for unnecessary (orphaned) packages. By default deborphan searches for orphaned libraries, but you can have it search for other types of packages also: data packages, dev packages, etc. by specifying one of its many --guess-* command line options.